Ramped cap unit for a main pool drain cover plate

Information

  • Patent Grant
  • 6397408
  • Patent Number
    6,397,408
  • Date Filed
    Monday, July 17, 2000
    24 years ago
  • Date Issued
    Tuesday, June 4, 2002
    22 years ago
Abstract
A ramped cap unit is provided for installation into a swimming pool in a position covering a main pool drain equipped with an upstanding antivortex safety drain cover plate, wherein the ramped cap unit has a smoothly contoured shape to permit a pool cleaner device to travel thereover without interrupting or obstructing cleaning operation. The cap unit comprises a generally inverted saucer defining a smoothly sloping and convex or ramped upwardly presented surface having a diametric size and shape to fit over the safety drain cover plate. An array of ribs formed on the underside of the cap unit engage an outer periphery of the upstanding cover plate to retain the cap unit in position thereon. A large plurality of vents are formed in the cap unit at spaced-apart locations to permit downward water flow therethrough substantially without disrupting the antivortex and safety functions of the underlying drain cover plate. The ramped upper surface of the cap unit permits a pool cleaner device to climb directly over the cap unit in the course of pool cleaner travel over submerged pool surfaces to collect and dislodge particulate debris settled thereon.
Description




BACKGROUND OF THE INVENTION




This invention relates generally to a ramped cap unit for use in combination with an antivortex or safety cover plate of the type installed over a main suction drain of a swimming pool or the like, wherein the ramped cap unit permits a pool cleaner device to travel directly over the ramped cap unit and the underlying safety drain cover plate without interrupting pool cleaning operation, and further without disrupting the antivortex and safety functions of the underlying safety cover plate.




Pool cleaner systems and related devices are generally well known in the art for use in maintaining residential and commercial swimming pools in a clean and attractive condition. In this regard, swimming pools conventionally include a water filtration system equipped with a pump for drawing or suctioning water from the pool for circulation through a filter canister having filter media therein to remove and collect water-entrained debris such as leaves and twigs as well as fine particulate including sand and silt. In a typical arrangement, at least a portion of the pool water is vacuum-drawn over a weir mounted within a so-called skimmer well positioned substantially at the water surface to draw and collect floating debris to the filter equipment, while another portion of the pool water is vacuum-drawn to the filter equipment through at least one so-called main suction drain located in the pool floor typically at a deep end thereof. From the filter canister, the water is recirculated to the pool via one or more return lines. Such filtration equipment is normally operated for several hours on a daily basis and serves, in combination with traditional chemical treatments such as chlorination or the like, to maintain the pool water in a clean and clear sanitary state.




The water filtration system is generally ineffective, however, to filter out debris which settles onto submerged floor and side wall surfaces of the swimming pool. In the past, settled debris has typically been removed by coupling a vacuum hose to the suction side of the pool water filtration system, such as by connecting the vacuum hose to the skimmer well located near the water surface at one side of the pool, and then manually moving a vacuum head coupled to the hose over the submerged pool surfaces to vacuum settled debris directly to the filter canister where it is collected and separated from the pool water. However, manual vacuuming of a swimming pool is a labor intensive task and is thus not typically performed by the pool owner or pool cleaning service personnel on a daily basis.




So-called automatic pool cleaner devices have been developed over the years for cleaning submerged pool surfaces, thereby substantially eliminating the need for labor intensive manual vacuuming. Such automatic pool cleaners typically comprise a relatively compact cleaner housing or head coupled to the pool water filtration system by a hose and including water-powered means for causing the cleaner to travel about preferably along a random path within a swimming pool to dislodge and collect settled debris. In one form, the pool cleaner is connected to the return or pressure side of the filtration system for receiving positive pressure water which powers a turbine for rotatably driving cleaner wheels, and also functions by venturi action to draw settled debris into a filter bag. See, for example, U.S. Pat Nos. 3,882,574; 4,558,479; 4,589,986; and 4,734,954. In another form, the pool cleaner is coupled by a vacuum hose to the suction side of the filtration system, whereby water is drawn through the pool cleaner to operate a drive mechanism for transporting the cleaner within the pool while vacuuming settled debris to the filter canister of the pool filtration system. See, for example, U.S. Pat. Nos. 3,803,658; 4,023,227; 4,133,068; 4,208,752; 4,643,217; 4,679,867; 4,729,406; 4,761,848; 5,105,496; 5,265,297; and 5,634,229. See also, copending U.S. Ser. No. 09/090,894, filed Jun. 4, 1998, and 09/176,532, filed Oct. 21, 1998.




In addition, in recent years, antivortex or safety cover plates have been developed for covering suction drains in a swimming pool or spa to reduce or eliminate the risk of suction-entrapment of a swimmer, particularly by suction-entrapment of a swimmer's hair or clothing. More specifically, the water filtration system pump is normally designed to draw water to the filtration equipment at a substantial flow rate and thus has the capacity to develop a significant suction or vacuum within filtration system flow lines. If a significant portion of the flow area of a suction drain is obstructed by a swimmer's hair or clothing or portion of the body while the filtration system is operating, the swimmer can be vacuum-drawn and retained at the drain with a substantial force to result in suction-entrapment of the swimmer and creating a risk of drowning. To safeguard against suction-entrapment accidents, many swimming pools are being constructed or retrofitted with an antivortex safety drain cover plate mounted over each pool suction drain and defining a geometric array of spaced-apart vents positioned to reduce or eliminate the risk of any significant portion of the vents being obstructed by a swimmer at one time.




Unfortunately, such safety drain cover plates typically project upwardly a short distance from the pool floor to define the multiple vents which may open in different directions, whereby the cover plate provides a raised obstruction to a pool cleaner as it traverses submerged pool surfaces to perform its desirable cleaning functions. In this regard, the pool cleaner can become trapped against the raised cover plate to interrupt normal cleaning operation.




The present invention relates to a relatively simple yet effective ramped cap unit for installation into a swimming pool in a position overlying an upstanding safety drain cover plate, wherein the cap unit is contoured to permit a pool cleaner to climb and travel directly thereover for uninterrupted cleaning operation, and further wherein the cap unit includes a large plurality of open flow vents to permit downward water flow therethrough substantially without disrupting the antivortex and safety functions of the underlying drain cover plate.




SUMMARY OF THE INVENTION




In accordance with the invention, a ramped cap unit is provided for installation into a swimming pool in a position covering a main pool drain equipped with an upstanding antivortex safety drain cover plate, wherein the ramped cap unit has a smoothly contoured shape to permit a pool cleaner device to travel thereover without interrupting or obstructing cleaning operation.




The ramped cap unit comprises a generally inverted saucer defining a smoothly sloping and convex or ramped upwardly presented surface having a diametric size and shape to fit over the safety drain cover plate. An array of ribs formed on the underside of the cap unit engage an outer periphery of the upstanding cover plate to retain the cap unit in position thereon, and to define a downwardly open central cavity into which the upstanding antivortex safety cover plate is nestably received. A large plurality of vents are formed in the cap unit at spaced-apart locations to permit downward water flow therethrough substantially without disrupting the antivortex and safety functions of the underlying drain cover plate. The ramped upper surface of the cap unit permits a pool cleaner device to climb directly over the cap unit in the course of pool cleaner travel over submerged pool surfaces to collect and dislodge particulate debris settled thereon.




In a preferred configuration, the ramped cap unit comprises a central disk having a size and shape corresponding generally with the size and shape of the safety cover plate. The central disk is assembled with an outer annular ring which may by formed from an assembled plurality of part-circle ring segments. Each ring segment has a plurality of vents formed therein to permit downward water flow therethrough to the underside of the annular ring into a plenum chamber in flow communication with vents formed in the safety cover plate. The annular ring tapers radially outwardly and downwardly from the central disk to an outer perimeter disposed substantially flush with the pool floor.




Other features and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.











BRIEF DESCRIPTION OF THE DRAWINGS




The accompanying drawings illustrate the invention. In such drawings:





FIG. 1

is a schematic representation of a swimming pool filtration system in combination with a suction-powered pool cleaner for cleaning submerged pool floor and side wall surfaces, and further illustrating the pool cleaner traversing a ramped cap unit embodying the novel features of the invention;





FIG. 2

is an exploded top perspective view showing the ramped cap unit for installation over an antivortex safety cover plate which is mounted in turn over a main pool drain;





FIG. 3

is an exploded top perspective view similar to

FIG. 2

, illustrating assembly of cap unit components;





FIG. 4

is an exploded bottom perspective view illustrating assembly of cap unit components;





FIG. 5

is a longitudinal vertical sectional view taken generally on the line


5





5


of

FIG. 2

, and depicted in exploded relation with an underlying safety cover plate mounted over a main pool drain;





FIG. 6

is a fragmented side elevational view depicting a pool cleaner in a position climbing onto the ramped cap unit;





FIG. 7

is a fragmented side elevational view similar to

FIG. 6

, but showing the pool cleaner in a substantially centered position on top of the cap unit; and





FIG. 8

is a fragmented side elevational view similar to

FIGS. 6 and 7

, but showing the pool cleaner in a position descending from the cap unit.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




As shown in the exemplary drawings, a ramped cap unit referred to generally in

FIGS. 1-8

by the reference numeral


10


is provided for mounting over an antivortex safety drain cover plate


12


which is mounted in turn over a main suction


14


drain located in a floor


16


of a swimming pool or the like as viewed in FIG.


1


. The ramped cap unit


10


is designed to provide a smoothly contoured profile shape to permit uninterrupted travel of a pool cleaner


18


over submerged pool surfaces to dislodge and collect particulate and debris settled thereon. In addition, the cap unit


10


is designed for compatibility with the safety cover plate


12


, to avoid disrupting the desired function of the safety cover plate in reducing or eliminating risk of suction-entrapment of any portion of a swimmer's body or clothing at the main drain


14


,




As schematically illustrated in

FIG. 1

, the swimming pool includes a conventional water filtration and cleaning system


20


to include a pump


22


for drawing water from the swimming pool for passage through a filter canister


24


having a selected filtration media (not shown) contained therein for capturing and collecting silt and grit and other particulate debris matter entrained in the water flow stream. The pump


22


draws a portion of the pool water through a skimmer well


26


which is normally mounted at one edge of the pool generally at the water's surface and includes a weir (not shown) over which water is drawn to skim and collect debris floating on the surface of the pool water. In addition, the pump


22


draws another portion of the pool water through at least one main pool drain


14


located in the pool floor


16


typically at a deep end of the swimming pool. The filtered water is recirculated from the filter canister


24


to the swimming pool through one or more return conduits


28


.




The pool cleaner


18


is coupled by a flexible hose


30


to the filtration system


20


and is adapted to be driven hydraulically to traverse submerged pool floor and side wall surfaces preferably in a random pattern to pick up and collect debris such as leaves and twigs as well as small particulate such as sand and silt settled thereon. The illustrative pool cleaner


18


is suction-powered by connecting the hose


30


to the suction side of the filtration system pump


22


, as by hose connection to the skimmer well


26


, wherein internal drive means (not shown) is hydraulically driven for rotatably driving one or more traction drive wheels


32


to transport the pool cleaner over submerged pool surfaces while additionally providing a suction cleaning flow to pick up settled dirt and debris for flow to the filter canister


24


. Alternately, it will be recognized and understood that other pool cleaners may be used of the type driven by a positive pressure water flow at the discharge side of the pump


22


. Exemplary suction-powered pool cleaners are shown and described in U.S. Pat. Nos. 3,803,658; 4,023,227; 4,133,068; 4,208,752; 4,643,217; 4,679,867; 4,729,406; 4,761,848; 5,105,496; 5,265,297; 5,634,229; and also in copending U.S. Ser. No. 09/090,894, filed Jun. 4, 1998, and Ser. No. 09/176,532, filed Oct. 21, 1998, all of which are incorporated by reference herein. Exemplary pressure-powered pool cleaners are shown and described in U.S. Pat. Nos. 3,882,574; 4,558,479; 4,589,986; and 4,734,954, which are incorporated by reference herein.




The ramped cap unit


10


comprises an enlarged and generally inverted saucer-shaped disk structure or saucer having a size and shape to rest on the pool floor


16


in a position overlying the safety cover plate


12


at the main drain


14


. In this regard, as shown best in

FIGS. 1-3

, the main drain


14


conventionally comprises an upwardly open passage formed in the pool floor


16


(

FIG. 1

) for suction flow of water from the pool to the filtration equipment


20


via appropriate flow lines


34


, as previously described. This drain passage


14


is covered by the antivortex safety drain cover plate


12


which upstands a short distance from the pool floor


16


and defines a plurality of open vents


36


arranged in a geometric pattern to reduce or eliminate risk of substantial obstruction of a significant portion of the open flow area at any one time by a swimmer, to correspondingly reduce or eliminate risk of swimmer suction-entrapment.

FIGS. 2-3

and


5


show the safety cover plate


12


upstanding from the pool floor


16


, wherein a peripheral outer rim


13


of the cover plate is elevated a short distance above the pool floor


16


(

FIG. 5

) to permit water flow through the array of vents


36


shown arranged circumferentially about said rim


13


to the main drain


14


. The upstanding safety cover plate


12


presents an obstruction to the pool cleaner


18


to potentially interrupt or stall pool cleaner travel throughout the pool to perform its desired cleaning functions.




The ramped cap unit


10


generally comprises an outer annular ring


37


formed from a plurality of part-circle ring segments


38


, three of which are shown in the illustrative drawings. These ring segments


38


are conveniently constructed from molded plastic each to include a large plurality of upwardly open vents


40


to accommodate downward water flow from above the cap unit


10


into an underlying plenum chamber


42


at the underside thereof. As shown best in

FIG. 4

, this plenum chamber


42


is subdivided by a plurality of circumferentially spaced, radially extending ribs


44


depending from the ring segments


38


. These ribs


44


extend radially outwardly from an inner peripheral margin of the annular ring


37


with progressively decreasing height and terminate at an outer peripheral margin thereof so that said outer peripheral margin of the annular ring


37


rests substantially flush on the pool floor


16


. Importantly, each ring segment


38


includes laterally projecting snap pins


46


at one side thereof, and laterally open snap ports


48


at an opposite side thereof, whereby the ring segments


38


can be snap-fit assembled to construct the annular ring


37


.




The cap unit


10


additionally includes a central disk


50


mounted on the outer ring


37


to extend over and close the region bounded by the inner peripheral margin of the ring


37


. This central disk


50


is also formed conveniently and economically from molded plastic or the like, and has a plurality of short protrusions


52


and


54


(shown best in

FIG. 4

) extending downwardly from the periphery thereof for mated and slide-fit reception into matingly shaped sockets


56


and


58


formed in an upper face of the ring segments


38


at the inner periphery thereof of the annular ring


37


. In the preferred form as shown, the protrusions


52


are round in shape for mating reception into round sockets


56


, whereas the protrusions


54


are square or rectangular in shape for mating reception into similarly shaped sockets


58


. Mounting screws


60


are desirably passed through selected ring sockets


58


and are fastened into mounting posts


62


on the underside of the central disk


50


to securely interconnect and assemble the outer ring


37


with the disk


50


. In addition, ballast weights


64


(

FIG. 5

) may be encased within small pockets


66


defined by the interfitting protrusions


52


and sockets


56


, to assist in retaining the assembled cap unit


10


on the pool floor


14


is a position substantially centered over the drain cover plate


12


. A series of vents


68


may also be provided in the central disk


50


to permit water flow downwardly to the underlying pool drain


14


. Alternately, in lieu of or in addition to the ballast weights


64


, the plastic material used for the ring segments


38


and/or the central disk


50


may be filled so that these components are relatively heavy and will thus remain seated on the pool floor over the drain cover plate


12


.




The diametric size of the assembled cap unit


10


is significantly greater than the diametric size of the underlying safety drain cover plate


12


mounted over the main pool drain


14


. When the cap unit


10


is placed in a substantially centered position over the main drain


14


and the associated upstanding cover plate


12


, the cover plate


12


fits into a downwardly open central cavity


70


(

FIG. 5

) defined cooperatively by the central disk


50


and the radially inner ends of the ribs


44


on the ring segments


38


. In this regard, the inner ends of these ribs


44


circumferentially surround the outer peripheral rim


13


of the cover plate


12


and thus are positioned to engage said outer rim


13


to prevent significant lateral shifting displacement of the cap unit


10


relative


20


to the upstanding cover plate


12


. Importantly, the large number of spaced-apart vents


40


formed in the ring segments


38


permit substantial downward water flow through the cap unit


10


to the vents


36


formed in the underlying safety cover plate


12


to avoid disrupting or interfering with the antivortex safety function thereof.




The geometric profile of the cap unit


10


permits unobstructed travel of the pool cleaner


18


throughout the swimming pool to perform its desired cleaning functions. In this regard, as shown best in FIGS.


1


and


6


-


8


, the outer peripheral margin of the cap unit


10


rests substantially flush on the pool floor


16


so as not to present any significant upstanding peripheral ridge or step which might otherwise obstruct cleaner travel. Moreover, the tapered height ribs


44


on underside of the ring segments


38


support the annular ring


37


in a manner defining an upwardly presented surface having a gentle incline relative to the pool floor


16


, wherein this incline forms a tapered ramp leading to the central disk


50


. This geometry enables the pool cleaner


18


to climb directly and easily onto and over the cap unit


10


, as shown in

FIGS. 6-8

, when the pool cleaner path of motion is intercepted by the cap unit.

FIG. 6

shows the pool cleaner


18


initially climbing onto the cap unit


10


, whereas

FIG. 7

shows the pool cleaner


18


is a position directly on top of the cap unit. Finally,

FIG. 8

illustrates the pool cleaner as it travels down the ramped cap unit to travel back onto the pool floor


16


.




A variety of modifications and improvements in and to the ramped cap unit


10


of the present invention will be apparent to those persons skilled in the art. Accordingly, no limitation on the invention is intended by way of the foregoing description and accompanying drawings, except at set forth in the appended claims.



Claims
  • 1. A ramped cap unit for use in a swimming pool to fit over a safety cover plate mounted over a pool drain formed in a submerged pool surface, wherein the safety cover plate upstands from the submerged pool surface, said ramped cap unit comprising:a generally inverted saucer having a central disk with a size and shape to fit over the safety cover plate, said central disk being assembled with a generally annular outer ring extending radially outwardly and downwardly from said central disk to define an outer perimeter adapted to rest substantially flush on the submerged pool surface when said central disk is fitted over the safety cover plate, said outer ring comprising a plurality of part-circle ring segments assembled together; said saucer being shaped to define a plenum chamber at an underside thereof in flow communication with the safety cover plate; said saucer having a plurality of vents formed therein to permit downward water flow from above said saucer to said plenum chamber; said saucer having a smoothly sloping upwardly presented surface to permit substantially uninterrupted travel of a pool cleaner thereover.
  • 2. The ramped cap unit of claim 1 wherein said ring segments include snap-fit means for retaining said ring segments in assembled relation.
  • 3. The ramped cap unit of claim 1 wherein said plurality of vents are formed in said outer ring.
  • 4. The ramped cap unit of claim 3 further including an additional plurality of vents formed in said central disk.
  • 5. The ramped cap unit of claim 1 wherein said central disk and said outer ring cooperatively define a downwardly open cavity for substantially nested reception of the safety cover plate.
  • 6. The ramped cap unit of claim 1 wherein said outer ring includes a plurality of downwardly extending and generally radially elongated support ribs each having a height decreasing in a radially outwardly direction, said support ribs being adapted to contact the submerged pool surface for spacing at least a portion of said outer ring from said submerged pool surface to define said plenum chamber.
  • 7. A ramped cap unit for use in a swimming pool to fit over a safety cover plate mounted over a pool drain formed in a submerged pool surface, wherein the safety cover plate upstands from the submerged pool surface, said ramped cap unit comprising:a generally inverted saucer having a central disk with a size and shape to fit over the safety cover plate and a generally annular outer ring extending radially outwardly and downwardly from said central disk to define an outer perimeter adapted to rest substantially flush on the submerged pool surface when said central disk is fitted over the safety cover plate; said saucer being shaped to define a plenum chamber at an underside thereof in flow communication with the safety cover plate; said saucer having a plurality of vents formed therein to permit downward water flow from above said saucer to said plenum chamber; said saucer having a smoothly sloping upwardly presented surface to permit substantially uninterrupted travel of a pool cleaner thereover; and further including ballast means carried by said saucer.
  • 8. The ramped cap unit of claim 7 wherein said central disk and said outer ring include interfitting members cooperatively defining at least one hollow socket, and further wherein said ballast means comprises a weight carried within said socket.
  • 9. A ramped cap unit for use in combination with an antivortex safety cover plate mounted over a drain opening formed in a floor of a swimming pool or the like, wherein the safety cover plate upstands from the pool floor, said ramped cap unit comprising:a generally inverted saucer having a central disk with a size and shape to fit over the safety cover plate, said central disk being assembled with a generally annular outer ring extending radially outwardly and downwardly from said central disk to define an outer perimeter adapted to rest substantially flush on the submerged pool surface at a location spaced radially outwardly from the safety cover plate when said central disk is fitted thereover, said outer ring comprising a plurality of part-circle ring segments assembled together; said outer ring being shaped to define a plenum chamber at an underside thereof and extending generally annularly about the safety cover plate in flow communication therewith; said outer ring having a plurality of vents formed therein to permit downward water flow from thereabove to said plenum chamber; said saucer having a smoothly sloping upwardly presented surface to permit substantially uninterrupted travel of a pool cleaner thereover.
  • 10. The ramped cap unit of claim 9 wherein said ring segments include snap-fit means for retaining said ring segments in assembled relation.
  • 11. The ramped cap unit of claim 9 further including a plurality of additional vents formed in said central disk.
  • 12. The ramped cap unit of claim 9 wherein said central disk and said outer ring cooperatively define a downwardly open cavity for substantially nested reception of the safety cover plate.
  • 13. The ramped cap unit of claim 9 wherein said outer ring includes a plurality of downwardly extending and generally radially elongated support ribs each having a height decreasing in a radially outwardly direction, said support ribs being adapted to contact the submerged pool surface for spacing at least a portion of said outer ring from said submerged pool surface to define said plenum chamber.
  • 14. A ramped cap unit for use in combination with an antivortex safety cover plate mounted over a drain opening formed in a floor of a swimming pool or the like, wherein the safety cover plate upstands from the pool floor, said ramped cap unit comprising:a generally inverted saucer having a central disk with a size and shape to fit over the safety cover plate and a generally annular outer ring extending radially outwardly and downwardly from said central disk to define an outer perimeter adapted to rest substantially flush on the submerged pool surface at a location spaced radially outwardly from the safety cover plate when said central disk is fitted thereover; said outer ring being shaped to define a plenum chamber at an underside thereof and extending generally annularly about the safety cover plate in flow communication therewith; said outer ring having a plurality of vents formed therein to permit downward water flow from thereabove to said plenum chamber; said saucer having a smoothly sloping upwardly presented surface to permit substantially uninterrupted travel of a pool cleaner thereover; said outer ring including a plurality of downwardly extending and generally radially elongated support ribs each having a height decreasing in a radially outwardly direction, said support ribs being adapted to contact the submerged pool surface for spacing at least a portion of said outer ring from said submerged pool surface to define said plenum chamber; and wherein said support ribs have radially inner ends cooperating with said central disk to define a downwardly open cavity for substantially nested reception of the safety cover plate.
  • 15. A ramped cap unit for use in combination with an antivortex safety cover plate mounted over a drain opening formed in a floor of a swimming pool or the like, wherein the safety cover plate upstands from the pool floor, said ramped cap unit comprising:a generally inverted saucer having a central disk with a size and shape to fit over the safety cover plate and a generally annular outer ring extending radially outwardly and downwardly from said central disk to define an outer perimeter adapted to rest substantially flush on the submerged pool surface at a location spaced radially outwardly from the safety cover plate when said central disk is fitted thereover; said outer ring being shaped to define a plenum chamber at an underside thereof and extending generally annularly about the safety cover plate in flow communication therewith; said outer ring having a plurality of vents formed therein to permit downward water flow from thereabove to said plenum chamber; said saucer having a smoothly sloping upwardly presented surface to permit substantially uninterrupted travel of a pool cleaner thereover; and further including ballast means carried by said saucer.
  • 16. The ramped cap unit of claim 15 wherein said central disk and said outer ring include interfitting members cooperatively defining at least one hollow socket, and further wherein said ballast means comprises a weight carried within said socket.
RELATED APPLICATION

This application claims the benefit of provisional application No. 60/146,295, filed Jul. 29, 1999.

US Referenced Citations (5)
Number Name Date Kind
3378858 Jacuzzi Apr 1968 A
4115878 Johnson et al. Sep 1978 A
4170047 Corsette et al. Oct 1979 A
4658449 Martin Apr 1987 A
5408706 Barnes Apr 1995 A
Provisional Applications (1)
Number Date Country
60/146295 Jul 1999 US